Popotosa Formation


The Popotosa Formation is a geologic formation in New Mexico. It preserves fossils dating back to the Neogene period.

Description

The Popotosa Formation is a thick sequence of volcanic debris beds with a few interspersed ash beds. It is exposed along the Rio Grande rift from the Socorro area. Radiometric dating of interbedded flows gives it an age of 26.4 to 7 Ma, corresponding to the late Oligocene to Miocene.
The formation is interpreted as deposition of fanglomerates and playa sediments in a closed basin in the early stages of rifting along the Rio Grande rift. It is thus typical of the lower Santa Fe Group.

History of investigation

The unit was first described by C.S. Denny in 1940, who named it for exposures near Canada Popotosa. It was assigned to the lower Santa Fe Group by Machette in 1978.

Footnotes